1. Field of the Invention
This invention relates to flow control apparatus and, more particularly, to in-line flow control valves for controlling the flow of a liquid through a conduit.
2. Description of the Prior Art
As is well known and understood, the valve art for controlling the flow of liquids is a relatively old art. However, the application of the valve art to the flow of intravenous solutions is somewhat limited. In the medical arts there are two primary types of mechanical flow control devices. One type is the screw clamp, and the other type is the roller clamp. The screw clamp includes a screw and a screw housing. The housing is situated so that as the screw is turned, the tip of the screw presses against the flat surface. Medical tubing, which is flexible, is disposed on one side of the flat surface against which the tip of the screw bears. Essentially, the tubing extends between a pair of flat surfaces, one of which is fixed and the other of which is movable by the screw. As the screw is tightened against the movable flat element, the flow through the tubing is restricted.
There are several problems associated with this type of clamp. For example, the clamp usually requires two-handed operation, one hand for holding the clamp and the other hand for adjusting the screw. Moreover, the clamp may slide up and down on the tubing, often within reach of the patient. As the patient moves, the motion of the tubing may cause the flow through the clamp to wander. Another problem is the lack of consistency of the medical tubing, both in terms of stiffness of the tubing and in the wall thickness of the tubing, which reflects the flow rate through the tubing.
The second type of clamp, the roller clamp, includes a roller in a track that is disposed adjacent to or above a flat incline. The medical tubing is run between the roller and the incline. As the roller is moved, it presses on the tubing and restricts the flow of fluid. The roller is spring biased against the tubing and the incline.
The roller type clamp can, like the screw clamp, move up and down on the tubing, often staying within the reach of the patient. As the patient moves, the motion of the tubing itself may cause a change in the position of the roller, which may result in a change in the flow rate to the tubing. The varying stiffness, or softness, of the tubing may cause the clamp to function in a normal manner, as designed, at times, and at other times may result in a flattening of the tubing, either restricting the flow substantially or even stopping the flow.
If the wall thickness varies, the incline may either not restrict the flow of fluid at all, or it may stop the flow. In order to compensate for this type of problem, the incline must extend over a relatively long distance, or else the rate of incline must substantially increase. Either alternative makes the clamp relatively bulky or eliminates some of the adjustment capability that a flow control device must have.
The in-line flow control valve apparatus of the present invention overcomes the problem of the prior art, as discussed above, by being insertable in the line or tubing. The flow of fluid or liquid is accordingly through the valve rather than through a restricted portion of the tubing or line itself.
While in-line flow control devices have not heretofore been developed for use in the medical field, flow control devices, using diaphragms, are relatively old and relatively well-known. Some examples of in-line diaphragm type valves are shown in the patents discussed below.
U.S. Pat. No. 1,800,157 discloses a diaphragm type valve with the diaphragm not directly connected to the actuator. Fluid pressure actuates the diaphragm to allow fluid to flow through the valve. The actuator is secured to a threaded rod and accordingly moves vertically as the threaded rod is rotated. The flow through the valve depends on two variables; one, the flow or the pressure of the fluid, and two, the position of the actuator.
U.S. Pat. No. 2,191,863 discloses a diaphragm valve with the diaphragm secured to the actuator. A threaded rod is secured to the actuator, and rotation of the rod accordingly results in vertical movement of the actuator. There is a relatively loose fit between the actuator and the threaded rod which allows relative movement therebetween, and accordingly a variation in the flow through the valve. Obviously, the precise control of the fluid flow through the valve is not of substantial importance with respect to the 2,191,863 patent.
U.S. Pat. No. 2,705,124 discloses a screw secured to a diaphragm and to a diaphragm actuator. Relative movement between the diaphragm and the diaphragm actuator is provided by a loose fit between the diaphragm actuator and a nut secured to the rod and held in place by the actuator. A threaded rod extends through the nut and into the diaphragm. As with the above patents, the precision control of fluid through the valve is ot of paramount importance.
U.S. Pat. No. 2,939,676 discloses another type of diaphragm valve in which a screw extends through a nut held in place by the valve housing. The screw is not secured to the diaphragm, but rather the nut, which moves vertically as the screw is turned, abuts a block secured to the diaphragm to limit the vertically upwardly movement of the block and accordingly of the diaphragm. Fluid pressure in the line causes the valve diaphragm to move until the nut is disposed directly against the block. The screw may be rotated to prevent flow through the valve, but if the screw is rotated to raise the nut, then the pressure of the liquid flowing through the line forces the diaphragm and the block away from the valve seat to allow the fluid to flow. As in the 1,800,157 patent, discussed above, the flow to the valve is a function of the pressure of the fluid flow in the line and the location of the nut secured to the threaded rod.
U.S. Pat. No. 2,953,346 is similar to the apparatus of the 2,191,863 patent, discussed above. A loose fitting nut is prevented from rotating and accordingly moves axially or vertically with respect to a screw which extends through the nut. The nut is secured by a relatively loose connection through the diaphragm actuator to provide vertical movement of the diaphragm for opening and closing the fluid passage through the valves. As with the other patents discussed above, the accuracy or precise control of the flow of liquid through the valve is not of primary concern with the apparatus of the 2,953,346 patent.
U.S. Pat. No. 3,275,291 discloses a diaphragm secured to a threaded sleeve which is in turn secured to a threaded rod. Rotation of the threaded rod causes the sleeve and the diaphragm to move vertically upwardly and downwardly. A relatively thin membrane is associated with the diaphragm, and the membrane and diaphragm together control the flow through a fluid passage in the valve. The membrane is not movable in response to the rotation of the threaded rod. Rather, when the diaphragm is moved away from the membrane, the pressure of the fluid causes the membrane to move away from its valve seat to allow the fluid to flow through the valve. The membrane includes an opening or aperture on its downstream side. When the downstream pressure exceeds the upstream pressure, fluid flows into a chamber between the membrane and the diaphragm and the pressure then causes the membrane to move to the valve seat to cut off the flow of fluid. The valve accordingly closes due to a pressure differential between the upstream and the downstream pressures when the upstream pressure is less than the downstream pressure. The diaphragm or the valve may also be closed when the diaphragm is moved vertically downwardly by rotation of the threaded rod. The downward rotation of the threaded rod causes the diaphragm to move downwardly against the membrane. As with the above patents, the precise control of the flow of liquid or flow through the valve is not of primary concern.
U.S. Pat. No. 3,666,230 discloses a valve in which a screw turns in a threaded portion of a valve body and allows fluid pressure to move a diaphragm against the screw. A second embodiment of the 3,666,230 apparatus utilizes a piston rather than a rotating screw to move a valve actuator either towards or away from the diaphragm. Fluid pressure on the piston allows the piston to move away from the valve actuator or toward the valve actuator, and the pressure of the fluid in the line through the valve results in the opening of the valve. As with the above patents, accuracy of flow through the valves is not of primary concern.
It will be noted that none of the above discussed patents are concerned with accuracy of flow of the fluid through a valve. Moreover, none of the patents is concerned with fluid flow for medical purposes. The apparatus of the present invention is primarily concerned with the precise control of fluid or liquid for medical purposes, using a diaphragm type valve to control fluid flow from one line to another with the assurance of maintaining a sterile fluid path.